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Journal of Applied Physics

Issue 10 • Date Sep 1966

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Displaying Results 1 - 25 of 61
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Determination of Mobility in Nonstoichiometric Low‐Mobility Semiconductors

    Page(s): 3647 - 3650
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    The method of determining charge‐carrier mobility by combining conductance with thermogravimetric measurements is discussed. The conditions of validity of the method are analyzed for one example. It is shown that the analysis of such measurements may permit estimation of an upper limit for the width of the conduction band. Application to CoO shows that the bandwidth in CoO is ≤kT at T=1500°K. View full abstract»

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  • Surface and Grain‐Boundary Diffusion of Gold‐Copper

    Page(s): 3650 - 3658
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    The diffusion of gold into copper grain boundaries from thin sources has been studied from 760° to 625°C. The activation energy for the grain‐boundary diffusion of gold into copper is 25 kcal/mole. At the lower temperature, there was observed surface depletion of gold at the grain boundary in accordance with theoretical solutions. The surface diffusion of gold on copper (100) surface was studied from 705° to 580°C under 10-9 Torr. The activation energy for surface diffusion was about 25 kcal/mole. The rates of surface diffusion were found to be less than those for grain‐boundary diffusion at the same temperature. Gold‐copper whiskers were generated adjacent to the grain boundaries for diffusion at or below 660°C. The growth of such whiskers is diffusion‐controlled and is attributed to the stress resulting from volume increase due to gold diffusion into the grain boundary. View full abstract»

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  • Effect of Structure on the Superconducting Properties of Eutectic Alloys

    Page(s): 3659 - 3665
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    The superconducting properties of twelve eutectic alloys have been studied. The seven alloys which were eutectics between terminal solid solutions were found to behave as type I superconductors irrespective of the solidification rate. Five other eutectic systems, all of which contained at least one intermetallic compound, were found to behave as type II superconductors. For the type II alloys a linear variation between the current‐carrying capacity and the interphase boundary area per unit volume was observed. Of the type II alloys, eutectics containing one superconducting and one nonsuperconducting phase were found to be more structure sensitive than those having both phases superconducting. View full abstract»

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  • Epitaxial Deposition of Germanium by Both Sputtering and Evaporation

    Page(s): 3665 - 3673
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    The structural characteristics of germanium films deposited onto germanium (111) and CaF2 (111) substrates have been characterized as a function of sputtering and evaporation parameters. Diagrams defining epitaxial temperatures and amorphous‐polycrystalline transition temperatures have been obtained both for sputtered and evaporated films. It is demonstrated that these transitions are a function of the growth rate and background pressure only. Neither the particular deposition conditions which control the growth rate (voltage and current in sputtering, source temperature, and source‐substrate distance in evaporation) nor the deposition techniques influence the transitions as long as the background pressure and growth rates are identical. A qualitative model based on the relation between growth rate and surface mobility is presented which appears to adequately describe the growth‐rate‐epitaxial‐temperature relations, including background pressure effects. The experimental data yield an activation energy for the onset of epitaxy at very low background pressures (evaporation) of 18 000 cal/mole, which is in good agreement with the activation energy for surface diffusion of germanium on germanium. Other activation energies ranging from 10 800 cal/mole at 65 μ argon pressure to 17 400 cal/mole at 8 μ argon pressure, have been obtained for sputtered films. The pressure dependence of the activation energy has been accounted for by the model presented. It is also demonstrated that the growth rates in all states of the film (amorphous, polycrystalline, and monocrystalline) are decreasing functions of substrate temperature. At any given temperature, the observed growth rates are dependent only on the incidence rate, and are independent of the technique (sputtering or evaporation) and of the conditions used to achieve the incidence rate. The dependence of growth rate on substrate temperature is consistent with es- tablished nucleation theory and yields activation energies for single‐crystal growth of approximately 10 000 cal/mole, for polycrystalline growth of approximately 3000 cal/mole, and for amorphous growth of approximately 600 cal/mole. These activation energies are independent of the deposition technique (evaporation or sputtering), the deposition conditions, and the incidence rate. View full abstract»

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  • Deposition of Tantalum, Tantalum Oxide, and Tantalum Nitride with Controlled Electrical Characteristics

    Page(s): 3674 - 3681
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    Results are presented which indicate that the effects of sputtering voltage and current on the resistivity of films sputtered from pure tantalum appear to be traceable to the pressures and growth rates associated with each sputtering condition. From these data it can be deduced that the observed resistance variations are largely accountable in terms of film impurity content. Tantalum sputtered reactively in the presence of oxygen produces films which are shown to exhibit a sharp transition from relatively low to very high resistivities as the oxygen concentration in the working gas is raised. Changes of greater than 12 orders of magnitude are observed. It is demonstrated that sputtering voltages and anode potentials effect a significant change in the transition point. Similarly well‐defined results are presented on films reactively sputtered in the presence of N2. The results tend to indicate that the anode potential retards (or enhances) electrostatically both the reactive and nonreactive interaction of tantalum with oxygen or nitrogen at the film surface. Results on the effect of substrate temperature on growth rate demonstrate that in reactive sputtering, the reaction occurs at the substrate surface. View full abstract»

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  • Step Motion on Crystal Surfaces

    Page(s): 3682 - 3686
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    It is postulated that steps on crystal surfaces capture atoms diffusing on the surface with certain probabilities and, in addition, that the capture probability depends on the direction from which adsorbed atoms approach the step. A general solution for the time‐dependent step distribution is obtained in terms of these probabilities and an arbitrary initial distribution of an infinite sequence of parallel steps. It is shown that coalescence of steps or stabilization of step spacings can occur as a consequence of assuming that capture probabilities are directionally dependent. Some of the implications of the theoretical model are related to the growth of real crystal surfaces. View full abstract»

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  • Local Mode Absorption in Compensated Silicon‐Doped Gallium Arsenide

    Page(s): 3687 - 3691
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    Infrared‐active localized vibrational modes in lithium‐ and copper‐compensated silicon‐doped GaAs are reported. A number of absorption peaks due to both Si and Li are seen at liquid‐nitrogen temperature. The local mode of the Si donor, SiGa, occurs at ν=384 cm-1; the Si acceptor, SiAs, at 399 cm-1. Two bands at 374 and 393 cm-1, along with a component of the 384‐cm-1 band, are tentatively identified as the SiGa bands split by a Li (or Cu) acceptor. The three corresponding Li bands are seen near 450 cm-1 with 7Li and near 480 cm-1 with 6Li. For Li(Cu)‐Si‐doped GaAs a weak coupling model between Si‐Li or Si‐Cu ion pairs is proposed. This model has been previously proposed for Li‐B‐doped Si. Si concentration studies indicate that the strengths of the SiGa 384‐cm-1 and SiAs 399‐cm-1 bands are related more closely to the total Si concentration than to the carrier concentration. A number of additional and, at present, unexplained peaks are also observed. View full abstract»

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  • Electron Diffraction Studies of the Epitaxy of Cu Single Crystals. I. Epitaxy of Evaporated Cu Films on Cu Crystals

    Page(s): 3691 - 3694
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    The epitaxy of evaporated Cu films on Cu single crystals has been investigated in situ under high‐vacuum conditions with reflection HEED techniques. Spherically shaped Cu single crystals with high quality surfaces were used as substrates. The effects of condensation temperature and the annealing behavior were studied for the main low‐index planes. A completely developed twin orientation of the film was found in all cases. For films deposited at room temperature the diffraction diagrams additionally contained a complete set of double diffraction spots. View full abstract»

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  • Electron Diffraction Studies of the Epitaxy of Cu Single Crystals. II. Early Stages of Epitaxy and Interfacial Dislocation Networks

    Page(s): 3694 - 3700
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    The first stages of epitaxy were investigated with reflection HEED methods for continuous Cu, Cu2O, and Ag films on Cu single‐crystal substrates. A new kind of diffraction pattern was obtained from the Cu{111} planes. It is produced by networks of interfacial dislocations. In case of the Cu layers, hexagonal arrangements of screw dislocations are formed in a pure twist boundary. The corresponding Burgers vectors are of the type ½〈110〉. For the Cu2O and Ag films, hexagonal and rhombohedric networks, respectively, of interfacial edge dislocations with Burgers vectors ⅙〈112〉 are probably present. The dislocation densities and modifications in the film lattice constants for the latter two epitaxial systems are in good agreement with values predicted by the theory of interfacial dislocations. View full abstract»

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  • Low‐Frequency Oscillations in a Thermal Cesium Plasma

    Page(s): 3701 - 3706
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    The oscillation modes present in the ``TOPSY'' thermally generated cesium plasma device have been investigated experimentally; oscillation frequency spectra and three‐axis (r,θ,z) maps of relative phase have been studied as functions of axial magnetic field strength, electron density, axial drift current, plasma column length, and ionizer sheath polarity. Both conducting and nonconducting cold end plates were used. Two distinct modes were observed: a low‐frequency oscillation (∼1 kHz) which was identified as an ion acoustic wave excited by axial circulating currents in the periphery of the plasma column, and a higher‐frequency oscillation (7 to 50 kHz) whose frequency behavior showed close agreement with the theory of the ``universal'' resistive drift‐wave instability, but which failed to show the azimuthal propagation predicted by this theory. The lack of observed azimuthal phase shift could not be explained in terms of the transit‐time‐controlled potential‐relaxation oscillations predicted for thermally generated plasmas, by sheath oscillations, or by the reflection of the drift waves at the plasma/end plate sheaths. Both modes were spontaneously present in the ``quiescent'' plasma (i.e., with no net drift current) and were neither further excited nor significantly altered in the presence of strong drift currents. View full abstract»

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  • Temperature and Strain‐Rate Dependence of the Flow Stress of AgMg Single Crystals

    Page(s): 3707 - 3713
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    The effect of temperature and strain rate on the flow stress of β‐AgMg single crystals was investigated in the temperature range of 77° to 900°K and strain‐rate range of 10-4 to 104 sec-1. The low‐temperature data were found to obey the predictions of the Peierls mechanism up to strain rates of 1.8×104 sec-1. Above strain rates of 1.8×104 sec-1 the shear stress becomes athermal and strain‐rate‐sensitive. The high‐temperature data were found to be thermally activated and showed increasing strength with decreasing temperature and increasing strain rate. There is a temperature‐sensitive, strain‐rate‐insensitive region which divides the low‐ and high‐temperature thermally activated mechanisms and shows increasing strength with increasing temperature. View full abstract»

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  • Nanosecond Breakdown in Liquid Dielectrics

    Page(s): 3713 - 3715
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    Measurements of nanosecond formative times in various liquids are summarized. The experiments utilized applied fields of up to 3.3×106 V/cm while equipment time resolution was on the order of 0.3 nsec. Detailed results are given for n‐hexane including aging time histories and formative times with and without an applied bias field. The data obtained in this study are compared with earlier work. Using a simplified breakdown model the mobility of charge carriers at 2×106 V/cm is calculated to be 8.7×10-2 cm2/V·sec. The nanosecond high‐voltage insulating qualities of various liquids are discussed. View full abstract»

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  • Effective Biaxial Anisotropy in Double‐Layered Thin Magnetic Films

    Page(s): 3715 - 3718
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    Quantitative experimental results have been obtained in support of a previously developed theory which represents the deformation of the critical curves of multilayered magnetic thin films in terms of effective multiaxial anisotropies. The effective biaxial anisotropy field has been experimentally observed to be proportional to the square of film thickness in the case of thinner films, as expected from the theory. From this dependence, the value of the exchange constant of Ni‐Fe‐Co (70–19–11 wt%) alloy is found to be A=1.6 ×10-6 erg/cm, which is in fair agreement with the value A=0.86×10-6 erg/cm obtained from a spin‐wave resonance measurement. Deviation from the quadratic dependence in thicker films has been observed and explained. View full abstract»

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  • High‐Sensitivity Magnetic Resonance by Bolometer Detection

    Page(s): 3719 - 3724
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    It is shown that spin magnetic resonance can be observed by a rise in the temperature of the sample, with a sensitivity equal to or better than with the more conventional electromagnetic detection methods. An experimental demonstration is provided by a crude bolometer made of a thin copper wire with a small sample of DPPH glued in the center. A sensitivity of about 5×1011 spins, for a detector bandwidth of 1 cps has been obtained at room temperature. An important advantage is the absence of a microwave carrier signal, resulting in a very stable baseline and the possibility of using very high microwave power. A detailed theoretical discussion shows that this method is well adapted for wide electronic lines, high frequency (up to 2‐mm wavelength), low temperature, and small size samples. In favorable cases (resonance of conduction electrons in metals or semiconductors) a sensitivity of 106 spins, at liquid‐helium temperature, is predicted. View full abstract»

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  • Simplified Theory of Reflectometric Thickness Measurement of Structured Soap and Related Films

    Page(s): 3725 - 3728
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    The intensity of reflected light is now used in the exploration of the structure of soap films, and of the forces responsible for it. An accurate interpretation must take into account the complicated sandwich structure of these films whose surfaces are formed by monomolecular layers upon an aqueous core. A direct simple approach assuming only that the surface layers are very thin compared to the wavelength of light shows that each layer of thickness d and refractive index n is optically equivalent to an increase of the thickness of the core having a refractive index m by a thickness d′=d(n2-1)/(m2-1), in agreement both with a physical picture of the phenomenon and with results obtained by more complicated calculations. This approach also permits immediate generalization to a structure formed by any number of very thin layers and also to closely related films of lipids in water which are used as model biological membranes. View full abstract»

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  • Interfacial Polarization in Single‐Crystal NaCl

    Page(s): 3728 - 3733
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    Capacitance and conductance dispersions and a dissipation factor maximum were observed in single‐crystal NaCl specimens at temperatures between 300° and 400°C. Probe measurements of the potential profile across these specimens in a dc field revealed the presence of a large potential drop in a very thin region adjacent to each electrode comparable in magnitude to the linear potential drop throughout the entire bulk of the crystal. The observed effects are shown to be consistent with an interpretation based on interfacial polarization arising from the presence of a surface layer having a higher resistivity than the bulk of the crystal. Interpretations based on dipole rotation or charge‐carrier blocking at the electrodes are shown to be in disagreement with the observed polarization data. View full abstract»

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  • Injection Electroluminescence in (AlxGa1-x)As Diodes of Graded Energy Gap

    Page(s): 3733 - 3740
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    p‐n junction diodes were made from AlAs‐GaAs mixed crystals of graded composition (energy gap). The energy gap vs composition was determined from measurements of the diode band‐edge emission peaks vs electron microprobe analysis of p‐n junction composition. A linear energy‐gap variation was observed throughout the composition range 0–0.45 mole fraction AlAs. Measurements of the injection‐current dependence and the temperature dependence of the emission spectra of these diodes, interpreted according to a simple model of injection electroluminescence, indicate that the AlAs‐GaAs mixed crystals are of direct band nature to at least 0.25 mole fraction of AlAs. Diodes of 0.40–0.45 mole fraction AlAs junction composition, i.e., in the vicinity of the ``direct‐indirect'' crossover, produced emission which requires more complex analysis. View full abstract»

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  • Thickness of Cs‐Sb Films Relative to the Original Sb Films

    Page(s): 3741 - 3743
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    A simple method of measuring the thickness of Cs‐Sb films in various compositions is described. The relation between composition ratio Cs/Sb and the increased thickness of the Cs‐Sb film relative to the original thickness of the Sb film is obtained. This relative thickness measured in Cs3Sb films is about seven, which agrees with the result predicted by the crystal structure of Cs3Sb. View full abstract»

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  • Effects of Gases on the Properties of Vapor‐Deposited Ni‐Fe Films

    Page(s): 3743 - 3750
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    Effects of O2, N2, H2, and H2O on characteristics of vapor‐deposited Ni‐Fe films are determined with the aid of quadrupole and monopole gas analyzers. Data obtained for films deposited in getter‐ion or oil‐diffusion‐type vacuum systems show that the presence of high oxygen partial pressures during deposition has a pronounced effect on the anisotropy field, coercive force, magnetoelastic strain coefficient, and product of easy axis dispersion and anisotropy field, while the other gases tested have little if any effect on film properties. High oxygen pressures or slow deposition rates during formation of the initial few‐hundred‐angstrom layer, followed by ``normal'' deposition, showed that propagation of a physical structure established in the initial layer is probably not responsible for the effects brought about by oxygen. Post‐deposition annealing in an oxygen‐rich atmosphere resulted in changes of magnetoelastic strain coefficient, indicating a surface oxide effect and/or diffusion into the films. ``Soaking'' glass substrates in high oxygen partial pressures for a short time prior to deposition did not have a noticeable effect on film properties, but treatment of substrates with oxygen‐bearing chemicals prior to deposition did cause significant changes in film properties. Attempts to find oxides in the Ni‐Fe films by electron‐diffraction techniques were unsuccessful, but microscopy studies revealed smallest grain size in films which were deposited in the presence of highest oxygen pressures. Electron‐diffraction analysis of pure nickel and pure iron films deposited in oxygen‐rich atmospheres showed the presence of NiO, FeO, Fe2O3, and Fe3O4. View full abstract»

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  • Simultaneous Giant Pulses from Five Ruby Laser Oscillators

    Page(s): 3750 - 3753
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    A laser system using bleachable‐filter Q‐switching has enabled us to obtain simultaneous ``giant pulses'' from five ruby laser oscillators. The beams from the different oscillators were found to be phase‐locked; the beam divergence was limited by the initial ruby quality. Two other systems for obtaining simultaneous giant pulses were investigated. One involved using the giant pulse from one oscillator to switch the bleachable cells in other oscillators; the other consisted of feeding the giant pulse from one oscillator into a branching chain of amplifiers. These latter systems proved less desirable for expansion to a large number of laser rods. View full abstract»

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  • High‐Temperature Internal Friction in Potassium Chloride

    Page(s): 3754 - 3766
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    A theory for the strain-amplitude-independent damping due to electrically charged dislocations oscillating within their surrounding charge clouds and for the strain-amplitude-dependent damping caused by the dislocations ``breaking away'' from their charge clouds is discussed. Damping experiments on single crystals of KCl [<100>, <111>, and <110> orientations] at temperatures of 450° to 760°C, frequencies ranging from 40 to 200 kc/sec, and strain amplitudes from 2.1×10-8 to 1.7×10-4 are reported. The damping φ in the amplitude-independent region could be represented by [open phi]=[open phi]0exp-(Eeff/kT), where Eeff is frequency-dependent and orientation-independent. At 750°C the amplitude-independent damping rose extremely rapidly with temperature; this rise is attributed to approaching the intrinsic isoelectric temperature. Amplitude dependence was found above a strain amplitude of 3×10-6 and the damping at high strain amplitudes was observed to decrease with time. The strain amplitude at which amplitude dependence was first detected did not vary noticeably with temperature or frequency. The experimental results are shown to be in general agreement with the proposed theory. View full abstract»

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  • Thermal Relaxation of Indium Films on Insulating Substrates between 4° and 300°K

    Page(s): 3767 - 3771
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    The thermal decay times of thin indium films evaporated on sapphire and quartz single‐crystal substrates have been measured over a range of temperatures which, with earlier measurements, now extends from 4°–300°K. At the higher temperatures the results were found to be in good qualitative agreement with the predictions of the thermal diffusion theory of heat transport, although there were some quantitative discrepancies. The decay times characterizing the initial part of the thermal decay of a 2200‐Å film on a sapphire substrate were measured to be as fast as ∼2×10-9 sec near 100°K, increasing to about 8×10-9 sec at room temperature. The decay times were found to be longest (up to ∼30×10-9 sec) below 10°K, where the heat transport is predominantly by ballistic phonon flow. The decay times for a 2700‐Å film on a quartz substrate were found to lie between 13 and 30×10-9 sec in the range of temperatures from 4° to 300°K. View full abstract»

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  • Thermodynamic Aspects of the Temperature—Pressure Phase Diagram of InTe

    Page(s): 3771 - 3774
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    The heat of transformation at one atmosphere from the metastable high‐pressure phase of InTe to the low‐pressure phase has been measured by metal solution calorimetry to be 0.44±0.01 kcal/g·atom and by differential scanning calorimetry to be 0.42±0.03 kcal/g·atom. These values are compared to the heat of transformation at 30 kbar obtained by applying the Clausius—Clapeyron equation to the temperature—pressure phase diagram of InTe. The volume change on fusion of the low‐pressure phase, InTe(I), at one atmosphere was measured to be 0.80 cc/mole. The initial slope of the liquidus in the phase diagram calculated using this value is in close agreement with the previously determined experimental slope. It is estimated that the triple point between the liquidus and the InTe(I)—InTe(II) phase boundary occurs at 718°C and 11 kbar. View full abstract»

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  • Exact Solution for the Eigenfrequencies of a Microwave Cavity Partially Filled with a Magnetized Plasma

    Page(s): 3775 - 3778
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    Pure TE and TM waves do not, in general, exist in a microwave cavity partially filled with a magnetized plasma. The scalar wave equations are coupled (the equation for Ez has a term involving Hz and vice versa). Uncoupling of the two equations results in two fourth‐order wave equations which are biquadratic. The solution of this equation can be obtained by factoring the fourth‐order expression into the product of two second‐order wave equations. The result is two solutions for Ez and Hz. From these terms, all other field components may be found. A set of six boundary conditions on the field components gives a determinantal expression for the eigenvalues. These can be presented in mode chart form and show the splitting of degenerate modes along with resonances at the electron‐cyclotron frequency. The technique is applicable to any form of the dielectric tensor if it can be specified in complex notation. View full abstract»

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Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

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Editor
P. James Viccaro
Argonne National Laboratory